Patent Document 1 discloses a composition for forming a ferroelectric thin film for forming one kind of ferroelectric thin film selected from the group consisting of PLZT, PZT, and PT, which is a liquid composition for forming a thin film formed of a mixed composite metal oxide in which a composite metal oxide B containing Ce is mixed with a composite metal oxide A represented by a general formula (PbxLay)(ZrzTi(1-z))O3. The liquid composition is a composition for forming a ferroelectric thin film formed of an organic metal compound solution in which a raw material for configuring the composite metal oxide A and a raw material for configuring the composite metal oxide B are dissolved in an organic solvent at a ratio so as to have a metal atom ratio represented by the general formula. In this composition for forming a ferroelectric thin film, x, y, and z in the general formula satisfy a relationship of 0.9<x<1.3, a relationship of 0≤y<0.1, and a relationship of 0≤z<0.9, respectively.
When a ferroelectric thin film is formed using the composition for forming a ferroelectric thin film configured as described above, it is possible to obtain a ferroelectric thin film which has substantially the same dielectric constant as that of a typical ferroelectric thin film and a low leak current density and the ferroelectric thin film which is suitable for a high-capacitance density thin film capacitor is obtained by a simple method. Accordingly, in a case where substantially the same level of leak current density as that of a typical ferroelectric thin film is obtained, a thinner film can be obtained and a higher dielectric constant is obtained.
It is known that piezoelectric properties are improved by adding Nb to a PZT-based thin film represented by PbZrxTi1-xO3 formed by using a sol-gel method (for example, see Non-Patent Document 1). In Non-Patent Document 1, effects exhibited when doping with Nb is performed on a {100}-oriented PZT-based thin film grown on a seed layer of PbTiO3 prepared by using a chemical solution deposition (CSD) method were investigated. Specifically, effects exhibited when doping with Nb within a range of 0 atom % to 4 atom % is performed on a {100}-oriented Pb1.1Zr0.52Ti0.48O3 thin film having a thickness of 1 μm were investigated. As a result, a high degree of {100} orientation of 97% was obtained in the entire film due to the incorporation of a Pb1.05TiO3 thin seed layer having a thickness of several nm. In addition, maximum polarization, residual polarization, squareness, and a saturated holding force of the entire PZT-based thin film were generally decreased together with a doping level of Nb. The PZT-based thin film doped with 3% of Nb shows the highest piezoelectric constant −e31.f of 12.9 C/cm2, which is higher than other thin films having other doping levels by 5% to 15%.